This prospective, randomized, controlled and multi-center study was performed in 6 closed intensive care units (ICU) of academic tertiary hospitals. Adult patients with septic shock admitted to the hospitals from 2005 to 2008 were assigned to the study eligibility. Eligible patients were centrally randomized using sealed envelopes into one of the three groups which included lactate, ScvO2, and control groups. The criteria of septic shock included two of four criteria for the systemic inflammatory response syndrome and systolic blood pressure lower than 90 mmHg or decrease of systolic blood pressure more than 40 mmHg after fluid challenge and the clinical signs of tissue hypoperfusion, including oliguria, blood lactate concentration of 4 mmol/L or more and consciousness alteration. The patients were excluded if they meet any one of follows: an age of less than 18 years, pregnancy, an acute cerebral vascular event (Glasgow coma score < 5), acute myocardial infarction or acute coronary syndrome, massive pulmonary embolism, status asthmaticus, a primary diagnosed cardiac dysrhythmias, contraindication to central venous catheterization, active gastrointestinal hemorrhage, massive intraabdominal infective focus without drainage, severe bronchopleural fistula, seizure, during chemotherapy or immunosuppressive therapy, or end stage of the diseases.